• 한국연소학회:학술대회논문집
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• 2005.10a
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• pp.132-137
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• 2005

The burning characteristics of interacting spherical droplet in a turbulent flow are numerically investigated. The transient combustion of 3-dimensionally arranged droplets, both the fixed streamwise droplet distances of 3 radii and 10 radii and different turbulence intensities, is studied. The results obtained from the present numerical analysis show that droplet vaporization rate for heptane droplet is insensitive to turbulence intensity, and that the transient flame configuration and retardation of droplet surface temperature augmentation with streamwise droplet spacing substantially influence vaporization process of interacting droplets. Single flame mode in which individual flames are merged into single flame, with decreasing streamwise droplet spacing, becomes faster. Therefore, vaporization rate of the second droplet with decreasing streamwise droplet spacing decreases remarkably with flame movement.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.69-75
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• 2004

The present study is numerically investigated for the high pressure effects on the vaporization process of the DME droplet. The evaporation rate of DME droplets is about twice that of dodecane droplets at the same chamber condition. The DM droplet vaporization characteristics is parametrically studied for the wide range of the operating conditions encountered with the high pressure combustion process.

• Journal of the Korean Ceramic Society
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• v.19 no.3
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• pp.193-198
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• 1982

The vaporization of $MgFe_2O_4$ was studied in $H_2-CO_2$ atmosphere over the temperature range of 600 to 90$0^{\circ}C$ by means of the transpiration method. It was found that the rate of vaporization for $MgFe_2O_4$ is controlled by a first order phase-boundary chemical reaction. The obtained activation energy of vaporization is 17.1 Kcal/mol.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.155-164
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• 2004

In order for studying pressure-coupled dynamic responses of droplet vaporization, open-loop experiment of an isolated droplet vaporization exposed to pressure perturbations in stagnant gaseous environment is numerically conducted, Governing equations are solved for flow parameters at gas and liquid phases separately and thermodynamic parameters at the interfacial boundary are matched for problem closure. For high-pressure effects, vapor-liquid interfacial thermodynamics is rigorously treated. A series of parametric calculations in terms of mean pressure level and wave frequencies are carried out employing a n-pentane droplet in stagnant gaseous nitrogen. Results show that wave instability in view of pressure-coupled vaporization response seems more susceptible at higher pressures and higher wave frequencies. Mass evaporation rate responding to pressure waves is amplified with increase in pressure due to substantial reduction in latent heat of vaporization. Augmentation of perturbation frequency also enhances amplification due to the reduction of phase differences between pressure perturbation and surface temperature fluctuation.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.1
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• pp.77-84
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• 1994

The oil crises in 1973 and 1978 stimulated the alternative fuel research activities in many countries around the world. Among the alternative fuels, methanol is one of the highest potential fuels for transportation. Methanol has been considered for use as automotive fuel, but it has a defect of the great latent vaporization heat. Therefore, authors have made the fuel vaporizing device in order to eliminate the fuel film flow heating the mixture. This paper presents a study on the characteristics of vaporization, engine performance, and emission which result from using the fuel vaporizing device.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1273-1281
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• 2003

The present study is mainly motivated to investigate the vaporization, auto-ignition, and combustion of liquid fuel spray injected into high pressure environment. The unsteady, multi-dimensional models were used for realistic simulation of spray as well as prediction of accurate ignition delay time. The Separated Flow (SF) model which considers the finite rate of transport between liquid and gas phases was employed to represent the interactions between spray and gas field. Among the SF models, the Discrete Droplet Model (DDM) which simulates the spray using finite number of representative samples of discrete droplets was adopted. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. In order to predict an evaporation rate of droplet in high pressure environment, the high pressure vaporization model was applied using thermodynamic equilibrium and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. In case of vaporization, an interaction between droplets was studied through the simulation of spray. The interaction is shown up differently whether the ambient gas field is at normal pressure or high pressure. Also, the characteristics of spray behavior in high pressure environment were investigated through the comparison with normal ambient pressure case. In both cases, the spray behaviors are simulated through the distributions of temperature and reaction rate in gas field.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.143-149
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• 2008

The present study is mainly motivated to investigate the vaporization, auto-ignition and spray combustion processes in DI diesel engine using DME and n-heptane. In order to realistically simulate the dimethyl ether (DME) spray dynamics and vaporization characteristics in high-pressure and high-temperature environment, the high-pressure vaporization model has been utilized. The interaction between chemistry and turbulence is treated by employing the Representative Interaction Flamelet (RIF) model. The detailed chemistry of 336 elementary steps and 78 chemical species is used for the DME/air reaction. Based on numerical results, the detailed discussion has been made for the distinctly different combustion characteristics of DME diesel engine in term of vaporization, ignition delay, pollutant formation, and heat release rate.

• 한국연소학회:학술대회논문집
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• 2001.06a
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• pp.106-118
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• 2001

A rigorous study of single droplet vaporization under quiescent high pressure atmosphere is attempted adopting method of flash evaporation calculation for vapor-liquid equilibrium. Results due to flash method shows excellent agreement with measurement. Also shown is the present model fairly capable of depicting transients of droplet vaporization under high pressure environment, such as ambient gas solubility, property variation, and multicomponent transports. Systematic treatment of these effects with emphasis on vapor-liquid phase equilibrium revealed; conventional treatment for subcritical droplet vaporization, such as $d^2$-law, leads to erroneous prediction of droplet history, augmented gas solubility is significant under supercritical pressure, and vaporization rate proportionally increase with pressure.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.193-207
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• 2002

The present study is mainly motivated to investigate the vaporization, autoignition, and combustion of liquid fuel spray injected into high pressure environment. In order to represent these phenomena realistically, discrete droplet model (DDM) which simulates the spray using finite number of representative droplets was adopted for detailed consideration of the finite rate of uansport between liquid and gas phases. The Eulerian-Lagrangian formulation was used to analyze the two-phase interactions. The high pressure vaporization model was applied using the thermodynamic and phase equilibrium at droplet surface. The high pressure effect as well as high temperature effect was considered in the calculation of liquid and gas properties. The characteristics of spray in high pressure environment were explained by comparison with normal pressure case.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.3
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• pp.33-44
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• 1983

This paper deals with the experimental study on the behavior of fuel (methanol) in intake manifold by using the basic apparatus which is manufactured the visible straight tube type model. In this study, the new device for liquid film thickness measurement and vaporization rate measurement are introduced to investigate the variation of liquid film thickness along the intake manifold and to observe the effect of vaporization of injected fuel. the results are summarized as follows: 1) The vaporization rate increases in proportion to decreasing of throttle valve angle and growing air fuel ratio. 2) The liquid film thickness along the intake manifold is mostly independent for the throttle valve angle in low air velocity and then affected in high air velocity, but the distribution of the liquid film thickness on circumferential position almost constant in the region of 300mm down stream from carburetor. 3) The mean liquid film thickness is 0.04 - 0.18mm in case of methanol in the region of air velocity Va = 12m/s - 55m/s and decreases with decreasing the throttle valve angle.